The Epidemiology Core of the HRCA/Harvard RNH will be the foundation for the program project in that it will assemble and maintain a cohort of older persons who will be involved in all 3 of the projects during the grant period. Over the previous four 5-year cycles of this grant, projects have recruited convenience samples from our volunteer subject registry, newspaper advertisements, nursing homes, and community housing sites. We are now undertaking a more generalizable approach by designing a population-based recruitment strategy. We will use door-to-door recruitment of a sample from a limited geographic radius surrounding the HRCA in collaboration with the University of Massachusetts, Boston, Center for Survey Research. The Epidemiology Core of the Harvard/HRCA RNH will recruit the sample, perform baseline and two annual follow up assessments conducted in the home and at the HRCA, will provide subjects for all three projects, and will use all available strategies to maximize retention of the cohort during the duration of the project. The specific aims of this Core are (1) to recruit a diverse, elderly (70 years of age and older), population-based sample from a defined geographic area surrounding the HRCA in Boston. This will be accomplished using census block sampling and door-to-door recruitment. Using both in-home and center-based visits, the core will characterize participants' baseline clinical, functional, and cognitive conditions; measure their gait, balance, cerebrovascular reactivity, orthostatic blood pressure, presence and features of pain, sensory function, and falls risk. Appropriate subjects will be referred to each of the three projects. All subjects will be followed for the occurrence of falls over 2 years of follow up using fall diary methods. Maximal follow up until death of participants or the end of the study period will be achieved using all available retention techniques. (2) This core will also continue to maintain and expand a registry of subjects interested in laboratory-based research, and will disseminate information to the population through its newsletter and seminars. This is a significant project for several reasons including the population based recruitment using door to door techniques, the assessement of novel risk factors and mechanisms of falls, the potential benefits to the community surrounding the HRCA and the creation of a valuable database to foster future research beyond the scope of this proposal.